139736eo.pdf (20MB) - Japan Oceanographic Data Center

oundaries between regions completed by different authors are distinctly visible. The tracks markedon the maps, therefore, make it possible to evaluate a single researcher’s interpretation for the wholeocean or a part of it. The maps by KANAEV et al. (1 977) and FISHER et al. (1 971) are an exampleof such reinterpretations.During the closing stages of IIOE and during the Upper Mantle Project, the study of key areaswas conducted through a combination of geophysical and geological methods. For example, detailedresearch was conducted by the Soviet expeditions in the rift zones of the Red Sea (MONIN et al.,1980) and in the zones of faults of the Karlsberg Ridge (ZHIVAGO, 1982). A number of otherexpeditions also worked in the Red Sea and on the West-Indian Ridge (WHITMARSH et al., 1974;SCLATER et al., 1981).OTHER MAPPING ACTIVITIESThe so-called aseismic rises are characteristic features of the Indian Ocean that have drawnmuch attention lately, for example the 54th and 58th cruises of the Research Vessel “Vityaz” on theNinetyeast Ridge, and studies of other expeditions on the Mascarene, Chagos-Laccadive, Madagascarand Broken Ridges and on Kerguelen Plateau (HOUTZ et al., 1977; FEDOROV and DANILOV,1978; GOSLIN et al., 1980; UDINTSEV and KORENEVA, 1982; AGAPOVA et al., 1983;BEZROUKOV and NEDPROCHNOV, 1983). These rises provide one of the keys to understandingthe tectonics and history of formation of the ocean bottom and the “ocean-continent” transition zone.The study of transition zones also has economic interest, particularly with respect to petroleum.Extensive geophysical research has been carried out off the coasts of Australia (VEEVERS et al.,1974; VEEVERS and COTERILL, 1978) and India (NAINI and TALWANI, 1983), in the Bay ofBengal (CURRAY and MOORE, 1974) and on the Mascarene Ridge (KAMEN-KAYE andMEYERHOFF, 1980).A certain amount of research has been done in the basins, where special interest has beenfocused on the fault zones (the so-called intraplate deformations). This kind of work was undertaken,for example, in the Central, Cocos and Oman basins (EITTREM and EWING, 1972; LARSON et al.,1978; BEZROUKOV and NEPROCHNOV, 1983).Maps showing bathymetry, magnetics and gravity, and geology, as well as is0 ach mapsoften are prepared within specific areas and then compiled into larger-scale maps. The 5 tR edition ofthe GEBCO chart (scale 1:lO million) is such a generalization of bathymetric data, in which plottingsheets were at the scale 1: 1 million. The sheets of the map were issued as soon as they were ready forpublication, often resulting in considerable differences in dates of issue. Sheet 5.05, covering theocean north of the equator, was published under the editorship of A.S. Laughton in April 1975,whereas sheet 5.09, covering the central part (from 0” to 47”s) and edited by R.L. Fisher, M. Yantschand R. Komer, was published in April 1982. Actually the map of the northern part of the ocean ispractically identical to the map in the International Geological-Geophysical Atlas. At present, the 6thedition of GEBCO is being prepared, its principal difference being the presentation of data in digitalform and preparation of computer-processed plotting sheets in scale 1 : 1 million.Regional magnetic field data have been represented mostly by plots of magnetic anomalieswhich have been used for different tectonic interpretations (LE PICHON and HEIRTZLER, 1968;McKENZIE and SCLATER, 1971). The gravity field data are published in a series of papers eithercovering the entire ocean ( BOWIN et al., 1982) or smaller areasbasins (SAITO and TAKEI, 1982;WHITE and ROSS, 1979; WHITMARSH, 1979; LUI et al., 1982; KIECKHEFER et al., 1981).Main features of the bottom topography, gravity and magnetic fields now can be mappedusing satellite-observed data (HAXBY et al., 1983; LANGEL et al., 1982; ENGELIS and RAPP,1984). These new possibilities are very attractive because such satellite missions have providedabundant information with uniform coverage, including remote areas poorly explored by surface ships.Generalized sediment isopach maps for large areas have not been made, except in the reviewvolume on the results of deep-sea drilling (HEIRTZLER, 1977) and by NEPROCHNOV (1979).Ocean bottom geology data were given in the Geological Atlas of the World (HEEZEN et al., 1978)and in SCHLICH’s (1982) monograph.82